SHARON SHANKS | The Cosmos Scientists seek help studying night skies

Amateur astronomers have two chances in the coming months to make valuable contributions to the scientific community. One involves watching a comet; the other involves the exciting world of extra-solar planets.
Of all the sciences, astronomy and geology are the most open to amateurs. And, of the two, the field of astronomy is the only one that actively seeks and relies upon the contributions made by the countless proficient and dedicated observers for whom astronomy is a passion, not a job.
Help wanted: Amateurs, professional astronomers with free telescope time and private observatories are being sought by the Deep Impact Mission to gather information on Comet Temple 1, target of the first space probe launched to a comet. The mission will be launched January 2004 and reach Temple 1 July 2005.
The science team behind the probe is seeking the most data on Temple 1 as possible to better understand such properties as its rotation rate and how fast it is producing dust. The more they know about the comet, the better they can design their spacecraft and instruments, including a probe that will be launched into the nucleus of the comet itself.
Owners of small telescopes can provide information on the lifestyle of an active comet. Comets far away from the warming influence of the sun tend to be quiet. When they reach the vicinity of the sun -- about the neighborhood of Mars -- they become active and begin & quot;outgassing. & quot; The frozen ices and gases that form much of their nucleus warm, and as they & quot;thaw, & quot; they lose material. We see something similar here on Earth when a piece of dry ice (frozen carbon dioxide) is exposed to air. The dry ice sublimates, or transforms from a solid directly to a gas.
Comet facts: The rate at which a comet loses material is determined by its composition -- how many gases there are and how much, what percentage is ice and how much is rocky material. By watching the coma -- the dusty & quot;shroud & quot; that hides the nucleus from our sight -- and the tail develop and change brightness, amateur astronomers can provide clues about the comet's size and composition.
The effort to gather material is part of the Small Telescope Science Program, started shortly after Temple 1 reached its perihelion, or closest approach to the sun, in February 2000. Observers watched through March of this year, when the comet became too faint to be seen by small telescopes.
The Deep Impact Mission is gearing up again for the return of the comet to our neighborhood. Temple 1 is a short period comet, taking only five years to make to make one orbit. It was discovered by Ernst Wilhelm Liebrecht Tempel of Marseille, France, in 1867.
Other discoveries: Until the advent of computer-controlled telescopes devoted to scanning the skies for near-Earth objects, amateur astronomers discovered nearly every comet. Amateur astronomer Tom Bopp, a Youngstown native who now resides in Arizona, co-discovered Comet Hale-Bopp, now one of the most famous and best-studied comets in history.
Area astronomers interested in taking part can check the Deep Impact home page at http://deepimpact.umd.edu. The page includes minimum telescope and filter requirements and the necessary CCD equipment as well as the observing schedule. In addition to watching Temple 1, amateur astronomers are also being sought to observe a star and possibly spot a planet moving across its face.
The call for observations has been made by the American Association of Variable Star Observers and involves the red dwarf Gliese 876, also known as IL Aqr in the constellation of Aquarius.
Astronomers will be looking for transits by either of the star's two massive planets. When a planet transits a star the light from the star dims slightly, an amount so small it can be measured only by very sensitive CCD or photoelectric photometry instruments. Both can measure the amount and intensity of light.
The first good chance to watch the star and possibly spot the transits was Wednesday. More opportunities will continue through May 27.
Information gathered can provide more details about the star's radius, mass and density and the orbits of its two Jupiter-size planets. They were discovered by a team led by Geoff Marcy, one of the top names in the new field of astronomy that searches for extra-solar planets.
Marcy uses a doppler shift method to look for planets around other stars, measuring the tiny shift in light as the pull of a planet swings a star toward or away from us, similar to the change in sound made when a firetruck's siren approaches us and then pulls away. But as equipment improves the transit method is also becoming more popular, and can be used to confirm the existence of a suspected planet.
In 1999 astronomers confirmed the existence of a planet around the sun-like star HD 209458, located 150 light years away from Earth.
XMore information about observing Gliese 876 is available from the AAVSO's home page at www.aavso.org/.